Unexplained CPU/DRAM Base frequency change in BIOS causing divide error.

We have MS-DOS 6.22 running a proprietary software program on a Pentium 166 MHz card slot main board on an ISA Bus back plane.  For it to run, the "CPU/DRAM base frequency" section of the BIOS must be set to "66/66MHz".
What can cause that to change back to the default "H/W Trap" with no other changes to the BIOS. We have ruled out user interface.
georgeraudAsked:
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BazicCommented:
Hi!

It can be that HW trap is set to higher frequency than 66Mhz.

If it is, then wait states (set also in setup) can be not enough for your DRAM chips and then You can have even stranger things than "divide error". Then it is hardware problem.

Other possible reason is: some older programs had some loop calibration procedures. Those procedures are sensitive for cpu speed because of limited loop iterations. On newer machines those programs can hang, or write divide error or Runtime Error 200 messages because those loops are done to fast to measure their time execution (time is equal to 0). When program wants to divide some constans value by execution time then You can have an error...

In your situation can be - after setting to HW You reach the point when cpu is to fast...

regards
Bazic
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